Electrical switch responsive to sudden movements of an external element

ABSTRACT

An electric switch responsive to sudden movements of an external element, but not to slow movements thereof, comprises a pair of electrical contacts separated by a yieldable connection which causes one to move with the other, and a flowable material, such as silicone putty, tending to resist the movement of the one contact with the other, the flowable material being free-flowing under low stress but not under a sudden high stress, whereby under s sudden movement of the external element and the one contact, the flowable material resists the movement of the other while the yieldable connection yields, thus effecting actuation of the switch; whereas upon a slow movement of the external element and the one contact, the flowable material flows and permits the other contact to move therewith, thus not effecting actuation of the switch.

United States Patent [5 6] References Cited UNITED STATES PATENTS 4/1944Reynolds.......

[72] Inventors OriEven-Tov Savyon;

ZOO/61.44

Pinchas Dagan, Petach-Tikva, both of III. 2 345 771 [21] P 564):2,863,017 12/1958 Thatcher...,........1. [22] Flled June 24, 1970 2 902671 9/1959 Pm [45] Patented Jan. 11, 1972 Primary E.\'aminerR0bert K.Schaefer Assistant Examiner-M. Ginsbu At!orney- Benjamin J. Barish [73]Assignee Israel Aircraft Industries, Ltd. [32] Priority July 19, 1968 [33 Israel 38 mww m mwm nv wm o m ac M Pv SWEO oms o Vt m m m c o P I aummm flu mhu m .nm h w man w ..h u m w CMPH hn O usfi un wm n 0 name fc1+ T m m a m m a e Am. w n o m a 22 km nh m mw m P n 0 nl um 00 m U H 2.1 t, n2n 4u C8] [54] ELECTRICAL SWITCH RESPONSIVE TO SUDDEN MOVEMENTSOF AN EXTERNAL ELEMENT mits the other contact to move therewith, thusnot effecting actuation ofthe switch.

PATENTEDJANI 1 1972 3,634,638

ZOI I An V v :4:

INVENTOR ORI E\/ENTO\/ L: i PlNCHAS DAGAN ATTORNEY ELECTRICALSWITCHRESPONSIVE TO SUDDEN MOVEMENTS OF AN EXTERNAL ELEMENT This is acontinuation of application Ser. No. 842,1 l4, filed July 16, 1969.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to electrical switches, and particularly to electricalswitches responsive to movements or displacements of an externalelement.

2. Description of the Prior Art Many types of movement-responsive ordisplacementresponsive electrical switches are known. All or most of theknown ones, however, cannot distinguish between sudden or quick'movements on the one hand, and slow movements on the other. There aresome applications where it is desired to have the electrical switchresponsive only to sudden or quick movements, and to be nonresponsive toslow movements. For example, one such application would be in protectivesystems for wire-fenced areas, where it may be desired to actuate theprotective system (e.g. to provide a signal or sound an alarm) when thewire fence is-pulled or cut in order to gain entry, but not to actuatethe protective system when slow movements of the wire fence areinvolved, such as arising from the expansion or contraction of the wirebecause of temperature changes.

SUMMARY OF THE PRESENT INVENTION An object of the present invention isto provide a simple electrical switch which is responsive to suddenmovements of an external element but is nonresponsive to slow movementsof the element.

According to the invention, there is provided an electrical switchresponsive to sudden movements of an external element, characterized inthat it includes a housing formed with an internal chamber containing afirst electrical contact adapted to be physically connected to theexternal element to be moved thereby, a second electrical contactmovable relative to the first contact to effect actuation of the switch,a yieldable connection between the first and second contacts tending tocause the latter to move with the former upon the movement of the formerby the external element, and a flowable material tending to resist themovement of the second contact with the first contact. The flowablematerial is free flowing under a low stress but not under a sudden highstress. The arrangement is such that a sudden movement of the externalelement causes the flowable material to resist the movement of thesecond contact with the first contact while the yieldable connectionyields, thus effecting actuation of the switch; whereas a slow movementof the external element causes the flowable material to permit themovement of the second contact with the first contact by the yieldableconnection, thus not effecting actuation of the switch.

The flowable material could conceivably be a liquid, e.g. a very viscousorganic dielectric liquid, or even a paste.

According to a further important feature of the invention, however, theflowable material is preferably silicone putty. This material has theappearance of ordinary putty but possesses a unique combination ofphysical properties. Under low stress it is plastic and free flowing andeven flows under its own weight. However, under sudden stress it acts asa solid; it will bounce when rolled as a ball and will even shatter likeglass. This material is known and has been commercially available for anumber of years. It is commonly used as a toy or novelty item and as anexerciser for crippled muscles. Particularly good results are attainedwhen it is used as the flowable material in the switch of the presentinvention. One product that may be used is that known as generalElectric G-E SS-9l Silicone Bouncing Putty."

Further features and advantages of the invention will be apparent fromthe description below.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is herein described, byway of example only, with reference to the accompanying drawings,wherein:

FIG. 1 is a longitudinal sectional view of an electrical switchconstructed in accordance with the invention; and

FIG. 2 is a top plan view of the switch of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The switch illustrated in thedrawings comprises a cylindrical plastic housing 2 formed with aninternal cylindrical chamber 4. The upper end of the chamber is closedby a cap 6 of resilient insulating material formed with an internalannular lip 8 adapted seat in an annular groove in the housing wall. Thelower end of chamber 4 is closed by walll0.

A metal rod 12 passes through resilient cap 6 and is anchored within thecap by a pair of annular rings 14 and 16 fixed to the rod. A metal pin18 is fixed to the lower ring 16 and serves as one of the electricalcontacts of the switch. The second electrical contact is in the form ofa metal sleeve 20 supported by a resilient insulating sleeve 22 which isa continuation of resilient cap 6, contact 20 being normally supportedaround, and out of engagement with, contact 18. The lower end of contact20 is tapered as shown at 20. An electrical conductor 23, connected tothe lower end of contact 20, passes through wall 10 and is connected toa terminal 24 fixed within a recess 26 at the bottom of the housing.

Terminal 24 is fixed to a metal bracket 28 used in mounting the switchto a support, e.g. post 29, and also in making an electrical connectionto the switch. Recess 26 is filled with a plastic material, such as anepoxy resin, to insulate terminal 24 and also to reinforce the mountingof bracket arm 28 to the housing. The switch mounting also includes asecond metal arm 30 embedded in a midportion of housing 2.

Within the chamber 4 of the housing there is disposed the flowablematerial 32 namely the silicone putty mentioned earlier. This materialfills chamber 4 to the level of the upper end of switch contact 20.

This upper end of metal rod 12 protruding through resilient cap 6 isadapted to be physically connected to the external element whose suddenmovement is to be sensed. For example, this external element may be awire 34 of a fence, as briefly mentioned earlier, and for this purposethe upper end of rod 12 carries a clamping element or hook 36 adapted tobe clamped or hooked to the wire.

The operation of the switch will be apparent from the foregoingdescription. Assuming that the switch is to be used for sensing thesudden movement of wire 34 of a fence, bracket arms 28 and 30 would bemounted to pole 29 of the fence with clamp 36 engaging the wire. Oneside of the electrical circuit (e.g., a signalling or alarm circuit)would be connected to the wire 34; and the other side would be connectedto the metal bracket 28 or to the post 29, if metal.

Under normal conditions, contact 18 is spaced from contact 20, andtherefore this electrical circuit is open. When a stress is applied towire 34, clamp 36 is permitted to pivot by resilient cap 6, this alsocausing electrical contact 18 to pivot. Contact 20, being mounted tocontact 18 by means of resilient insulating sleeve 22 which acts as ayieldable connection, also tends to move with that contact, but thismovement is opposed by the flowable silicone putty 32.

Now, if the movement of wire 34 is sudden and large, such as would beproduced by someone pulling or cutting the wire to gain access into theprotected area, a high stress is produced in the flowable silicone putty32. Since this material is not free flowing under high stress, it willresist the movement of contact 20 with contact 18. Contact 18 will thusengage contact 20, while the resilient sleeve 22 yields, and the switchwill be actuated to sound the alarm or to provide the signal.

On the other hand, if the movement of wire 34 is very slow, such aswould be produced by the expansion or the contraction of the wire duringchanging temperature conditions, or by the wind, the flowable siliconeputty 32 is subjected to a low stress. This material being relativelyfree flowing under low stresses, it will not prevent the movement ofcontact 20 with contact 18 by resilient sleeve 22, and thus the twocontacts will be held apart, and the switch will not be actuated.

Many changes, variations and other applications of the illustratedembodiment of the invention will be apparent.

What is claimed is:

1. An electrical switch responsive to sudden movements of an externalelement, characterized in that it includes a housing formed with aninternal chamber containing a first electrical contact adapted to bephysically connected to said external element to be moved thereby, asecond electrical contact movable relative to said first contact toeffect the actuation of said switch, a yieldable connection between saidfirst and second contacts tending to cause the latter to move with theformer upon the movement of the former by said external element, and aflowable material tending to resist the movement of saidsecond contactwith said'first contact, said flowable material being substantially morefree flowing under a low stress than under a'sudden highstress, wherebya sudden movement of the external element causes the flowable materialto resist the movement of said second contact with said first contactwhile said yieldable connection yields, thus effecting actuation of saidswitch, whereas a slow movement of the external element causes theflowable material to permit the movement of said second contact withsaid first contact by said yieldable connection, thus not effectingactuation of said switch.

2. An electrical switch as defined in claim 1, wherein said flowablematerial is silicone putty.

3. An electrical switch as defined in claim 1, wherein said secondcontact is a metal sleeve, and said yieldable connection is a resilientinsulating sleeve normally supporting said second contact around and outof engagement with said first contact. I

4. An electrical switch as defined in claim 3, wherein said resilientsleeve is carried by a resilient cap closing the upper end of saidhousing, said resilient cap supporting said first contact in suspensionand including a rigid member passing therethrough and adapted to beconnected to said external element.

5. An electrical switch as defined in claim 4, wherein said flowablematerial fills said housing chamber to the level of said second contact,the latter being tapered at its lower end.

6. An electrical switch as defined in claim 1, further including a metalbracket arm attached to the housing at the lower end thereof, therebeing an electrical connection between said second contact and saidbracket arm.

7. An electrical switch as defined in claim 6, further including asecond bracket arm attached to a midportion of said housing for mountingsame to a support.

8. An electrical switch as defined in claim 2, wherein said secondcontact is a metal sleeve, and said yieldable connection is a resilientinsulating sleeve normally supporting said second contact around and outof engagement with said first contact.

9. An electrical switch as defined in claim 8, wherein said resilientsleeve is carried by a resilient cap closing the upper end of saidhousing, said resilient cap supporting said first contact in suspensionand including a rigid member passing therethrough and adapted to beconnected to said external element.

1. An electrical switch responsive to sudden movements of an externalelement, characterized in that it includes a housing formed with aninternal chamber containing a first electrical contact adapted to bephysically connected to said external element to be moved thereby, asecond electrical contact movable relative to said first contact toeffect the actuation of said switch, a yieldable connection between saidfirst and second contacts tending to cause the latter to move with theformer upon the movement of the former by said external element, and aflowable material tending to resist the movement of said second contactwith said first contact, said flowable material being substantially morefree flowing under a low stress than under a sudden high stress, wherebya sudden movement of the external element causes the flowable materialto resist the movement of said second contact with said first contactwhile said yieldable connection yields, thus effecting actuation of saidswitch, whereas a slow movement of the external element causes theflowable material to permit the movement of said second contact withsaid first contact by said yieldable connection, thus not effectingactuation of said switch.
 2. An electrical switch as defined in claim 1,wherein said flowable material is silicone putty.
 3. An electricalswitch as defined in claim 1, wherein said second contact is a metalsleeve, and said yieldable connection is a resilient insulating sleevenormally supporting said second contact around and out of engagementwith said first contact.
 4. An electrical switch as defined in claim 3,wherein said resilient sleeve is carried by a resilient cap closing theupper end of said housing, said resilient cap supporting said firstcontact in suspension and including a rigid member passing therethroughand adapted to be connected to said external element.
 5. An electricalswitch as defined in claim 4, wherein said flowable material fills saidhousing chamber to the level of said second contact, the latter beingtapered at its lower end.
 6. An electrical switch as defined in claim 1,further including a metal bracket arm attached to the housing at thelower end thereof, there being an electrical connection between saiDsecond contact and said bracket arm.
 7. An electrical switch as definedin claim 6, further including a second bracket arm attached to amidportion of said housing for mounting same to a support.
 8. Anelectrical switch as defined in claim 2, wherein said second contact isa metal sleeve, and said yieldable connection is a resilient insulatingsleeve normally supporting said second contact around and out ofengagement with said first contact.
 9. An electrical switch as definedin claim 8, wherein said resilient sleeve is carried by a resilient capclosing the upper end of said housing, said resilient cap supportingsaid first contact in suspension and including a rigid member passingtherethrough and adapted to be connected to said external element.